It is known that an adult T cell leukemia virus (hereinafter referred to as "ATLV"), which has been isolated from patients with adult T cell leukemia (hereinafter referred to as "ATL"), infects immunocompetent cells and causes a variety of immunological disorders or decrease of immunological competence including ATL [cf. Proceedings of the National Academy of Science of the United States of America, 78, 6476 (1981)]. The nucleotide sequence of the gene of said virus is known [cf. Proceedings of the National Academy of Science of the United States of America, 80, 3618 (1983)]. For detection of the anti-ATLA antibody or preparation of vaccine for prophylaxis or treatment of ATL, a recombinant protein of ATLV-related antigen has been prepared by the gene engineering technique [cf. Japanese Patent Application Laid-open KOKAI No. 124963/1988; Gene, 38, 57 (1985); Proceedings of the National Academy of Science of the United States of America, 81, 6202 (1984)] or a synthetic peptide of ATLV-related antigen has been prepared by the peptide synthesis technique [cf. Journal of Immunology, 136, No. 7, 2393 (1986); Virology, 136, 338 (1984); Japanese Patent Application Laid-open KOKAI No. 301896/1988; Japanese Patent Application Laid-open KOKAI No. 30600/1986; Leukemia Research, 9, No. 9, 1111 (1985)].
Diseases caused by ATLV include those directly caused by ATLV such as ATL and HTLV-I associated myelopathy, and those indirectly caused by ATLV such as chronic pulmonary diseases, opportunistic pulmonary infections, M proteinosis, chronic renal failure, immunodeficiency (e.g. non-specific dermatomycosis, etc.), and the like. At present, ATL has been treated mainly by symptomatic therapy for those diseases having no subjective symptoms or for chronically progressing diseases or by chemotherapy using multiple drugs, especially anti-tumor agents, for progressive ATL. However, the effects of these methods are not clear, and hence, more improved method is desired for treating the above mentioned diseases more effectively and surely.
At present, the anti-ATLA antibody has been detected by an indirect immunofluorescence method in which ATLV-infected cells are coated onto a slide glass and the anti-ATLA antibody is detected using an antibody labelled with fluorochrome [Nature, 294, 770 (1981)], by a particle agglutination method utilizing the phenomenon that gelatin particles sensitized with ATLV or antigenic components thereof agglutinate in the presence of the anti-ATLA antibody [Gann, 7, 845 (1984)], by a radioimmunoassay using a microcup coated with antigenic components extracted from ATLV-infected cells [Journal of Experimental Medicine, 159, 1117 (1984)] or by an enzyme-linked immunosorbent assay (hereinafter referred to as "ELISA") [Gann, 74, 185 (1983)].
However, ATLV-infected cells and partially purified antigenic components obtained therefrom also contain various non-specific antigenic components. Therefore, when the anti-ATLA antibody is measured using these ATLV-infected cells or antigenic components thereof as a reagent, these reagents are also recognized by another non-specific antibodies in a specimen other than the target anti-ATLA antibody such as an anti-nuclear antibody and an anti-T cell antibody. As a result, the presence of the anti-ATLA antibody is not correctly determined by these methods.
For overcoming this problem, many studies have been made as to radioimmunoassay or ELISA using a recombinant protein or synthetic peptide. For example, methods using the recombinant protein include those using an env protein which is considered to have a high antigenicity [Science, 226, 1094 (1984); Proceedings of the National Academy of Science of the United States of America, 81, 6202 (1984); Japanese Patent Application Laid-open KOKAI No. 166624/1985; Japanese Patent Application Laid-open KOKAI No. 166699/1985], those using a gag protein [Gene, 38, 57 (1985); Japanese Patent Application Laid-open KOKAI No. 61534/1985; Japanese Patent Application Laid-open KOKAI No. 124963/1988] and the like. As the methods using synthetic peptide, there have been reported a radioimmunoassay using peptides corresponding to amino acid sequences of hydrophilic regions selected from the gag protein region or env protein region of ATLV, said peptides being synthesized by peptide synthesizer [Journal of Immunology, 136, No. 7, 2393 (1986); Journal of Immunology, 142, No. 3, 971 (1989); Proceedings of the National Academy of Science of the United States of America, 84, 2479 (1987)] and the like. Although these methods utilize the recombinant proteins or synthetic peptides which do not contain non-specific components, they are disadvantageous in that the recombinant proteins or synthetic peptides in these methods show only low specificity against the anti-ATLA antibody and that they are not safe due to the use of radioactive substances. Therefore, it has been desired to develop a method for measuring the anti-ATLA antibody which does not involve the use of radioactive substances and utilizes an antigenic polypeptide which is highly specific against the anti-ATLA antibody.